Summary
Located in the western pacific, the Mariana Trench is the deepest part of the ocean, plunging down 11km.
Down there it's pitch black, icy cold and the pressure is immense.
Now explorers with funding from the private sector are planning to return to the bottom of the Trench, for the first time for over 50 years.
Rebecca Morelle meets Jim Gardner, who works for the US Center for Coastal and Ocean Mapping, and has just completed the most detailed survey ever of the Mariana Trench, using sonar.
Alan Jamieson, an ecologist at Oceanlab at the University of Aberdeen in Scotland, uses remote controlled submersibles to study the animals and plants that live at extreme pressure in the deepest parts of the oceans.
He tells Rebecca why he believes it is preferable to deploy robots rather than humans to do this research.
Legendary marine biologist and underwater explorer, Sylvia Earle, argues that it is essential for us to visit the depths of the ocean and see the extraordinary environment with our own eyes.
As the former science chief for the National Oceanic and Atmospheric Administration, NOAA - the ocean's equivalent of NASA - Sylvia Earle says that the seas have always been the poor relation to space.
Rebecca finds out from Bill Raggio of precision glass company Rayotek in San Diego, how to build a glass sphere for Triton submarines which will stop the three-man crew from being crushed by the pressure a the bottom of the Mariana Trench.
And Sandra Brook from the Marine Conservation Biology Society talks about how research scientists may work with the commercial teams, like Triton, in the future as resources dry up for purely research submersibles.
Transcript
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| 0:00.0 | I'm Rory Stewart and I grew up wanting to be a hero and I'm still fascinated by the ideas of heroism. |
| 0:08.9 | In my new series, I'm taking in the long sweep of history from Achilles to Zelensky and asking, what is a hero? |
| 0:16.2 | Simply doing your job, being a decent human being. |
| 0:20.0 | A true hero is someone who just kind of shines by their own light, |
| 0:23.9 | and that light is to be recognised by others. |
| 0:26.5 | The Long History of Heroism with me, Rory Stewart. |
| 0:29.5 | Listen on BBC Sounds. |
| 0:32.6 | Thank you for downloading from the BBC. |
| 0:35.4 | For details of our complete range of podcasts and our terms of use, |
| 0:39.5 | go to BBCworldservice.com slash podcasts. |
| 0:47.4 | Half a century after the deepest part of the ocean was first conquered, |
| 0:55.8 | the race is on to return. |
| 1:02.8 | Four teams are getting ready to dive 11 kilometers down to the bottom of the Mariana Trench in the Pacific. |
| 1:09.5 | I'm Rebecca Morel, and in the last program I heard from the only man alive who's experienced these depths. |
| 1:15.2 | After we landed, we stirred up bottom sediment, and after 20 minutes, it was like looking in a bowl of milk, and we decided, well, we better go up. We're not going to be able to stay |
| 1:19.5 | here long enough to get a clear picture. And I met some of the explorers to find out why |
| 1:24.2 | they're risking it all to repeat his epic journey. It's about two hours and 20 minutes to the bottom, and that'll be in the glowing dark, |
| 1:31.3 | and I'll be trying to do that mostly with the lights off, trying to see as much as possible. |
| 1:35.3 | It's not just sort of a flag-planting exercise. The point is to really be able to reliably have craft |
| 1:41.3 | that are capable of going anywhere in the ocean that we choose to go. |
| 1:45.1 | We're exploring interspace. We're exploring a part of our planet that no one's ever seen before. |
| 1:49.8 | I think that's fascinating. In fact, I would venture to bet it's more exciting in some cases than |
... |
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